Published on 4th May, 2018
Spreading manures should not just be using up a by-product, but about fully utilising a valuable resource, says head of show, Alan Lyons. “Nutrient levels vary considerably, as do the application technology and regulations, so there’s more to this simple practice than just spreading it on the field. The key is to maximise nutrient availability by applying manure in optimum conditions, and thereby reduce the need for inorganic inputs.”
Matching manure applications to the soil nutrient status is crucial, advises John Williams at ADAS, who will be speaking in the muck demonstration area and seminars. “Muck and slurry should be used and treated as a fertiliser, rather than a waste product to just empty on fields. It does take investment in kit and management to do it well but it’s a wonderfully valuable source of nutrients.”
Every 40t/ha of cattle farm yard manure can be worth £220/ha in NPK value, he explains.
The first thing is to understand the nutrient content of the material. “Manures have hugely variable nutrient content and dry matter levels – and cow slurry compared to pig slurry will be very different because of the different feed intakes. The AHDB Nutrient Management Guide has averages for a number of organic manures and these typical figures are a good starting point,” says Mr Williams “Taking samples is the next step and it’s important to be representative when doing this. Try to homogenise the slurry in some way and take a number of samples to see how the content varies.”
Farmers then have to decide where to apply the muck. “With a typical application you will be supplying more phosphate and potash than the crop will need in one year, so repeat applications can lead to high levels,” he explains. “Therefore soil testing first can identify where best to put the manure.”
Application rates should be tailored to meet the crop’s nutrient demands. “This is reasonably straightforward for slurry as you’ll know what the tanker holds and the size of the field but it’s more difficult with solid materials as the bulk density and weight can vary – and newer material will take up more space than old.”
One way to approach application rates is to use a spreader which has weigh cells, but alternatively a weigh bridge can be used. “If you apply without knowing the weight, then you can’t know what the application rate is.”
Mr Williams also suggests making sure slurry and muck are spread as evenly as possible and that solids are incorporated within 24 hours to minimise smells and reduce nutrient losses. “Spring applications are better for nitrogen use efficiencies but you’ve got to be careful not to damage the soil. Also, the risk of run off and contamination is higher – so it’s important to get timings right. In the autumn it’s typically drier and applications are best done in September or October for crops that require autumn N, such as grass or oilseed rape – otherwise you risk leaching.”
Visitors will be able to see a large range of exhibitors at Grassland UK, enabling them to get the best advice on what is needed for their system. Whether you are looking for a new spreader, variable rate technology or more information on how to test manures and soils, there’ll be an opportunity to get questions answered or to see the latest kit demonstrated.